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F3--04ADS 4-Channel Isolated Analog Input
Standard 4 to 20 mA transmitters and transducers can operate from a wide variety of
power supplies. Not all transmitters are alike and the manufacturers often specify a
minimum loop or load resistance that must be used with the transmitter.
The F3--04ADS provides 250 ohm resistance for each channel. If your transmitter
requires a load resistance below 250 ohms, then you do not have to make any
adjustments. However, if your transmitter requires a load resistance higher than 250
ohms, then you need to add a resistor in series with the module.
Consider the following example for a transmitter being operated from a 36 VDC
supply with a recommended load resistance of 750 ohms. Since the module has a
250 ohm resistor, you need to add an additional resistor.
0V
+36V
DC Supply
Two-wire Transmitter
+
--
R
=
Tr
-
Mr
R -- Resistor to add
Tr -- Transmitter Requirement
Mr -- Module resistance (internal 250 ohms)
R
=
750
-
250
R
=
500
--
+
Module Channel 1
R
250
O
Current Loop
Transmitter
Impedance